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Questions tagged [digital-communications]

Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.

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Efficient Padding for UART to Minimize Power Consumption

So, I am implementing a custom protocol over UART (data field in the packet is fixed at 8 bytes + contains a len field). If the data len is less than 8 bytes, 0xFF is being used for padding. I ...
dsoham's user avatar
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Distinguishing light sources with STM32 ADC and fast fourier transform

I want to identify if there are other light sources present at the same time as a 5 kHz 50% duty cycle PWM LED is on (this is arbitrary and it can be modulated at a different frequency). I have an ...
donut's user avatar
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Is the probability transition matrix of M-PSK signaling in AWGN channel invertible?

Consider an AWGN channel with MPSK modulation, and let \$P=[p_{i,j}]\$ denote the corresponding transition probability matrix, where \$p_{i,j}\$ denotes the probability that symbol \$j\$ is detected ...
Ben's user avatar
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Exercise on PPM modulation bit rate

A digital communication system uses N=15 identical routes. The modulation used is 2-PPM. Calculate the value of $$ \varepsilon_b/N_0 $$ on the exit from the first route so that a final error ...
Gabriele's user avatar
5 votes
2 answers
168 views

Well protected digital input with long wires

I've created simple circuit to protect MCU's digital input against eg. induced spikes. I want to connect quite long wires to this HW and highly probable that this board will be placed close to the ...
szymo092's user avatar
1 vote
1 answer
216 views

Digital Beamforming performance issues - ADC and DAC clipping

Digital Beamforming when compared with analog beamforming provides many benefits in terms of performance and flexibility. It is however more complex and each antenna will have its own frontend and own ...
cesar's user avatar
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1 answer
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Rx digital beamforming

I am using Rx digital beamforming with independent ADCs . These ADCs introduce quantization noise which I am trying to calculate and model. I am not sure though if that quantization noise adds in ...
cesar's user avatar
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Computing channel capacity for channels types other than simple AWGN

My question is about computing capacity for comms channel models other than simple AWGN. For example, a very simple multipath channel (say line-of-sight + one path) plus AWGN. Are there any such non-...
gschro's user avatar
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Is FM ever used for digital radio transmission [closed]

The idea would be to transmit multiple bits(or frames) with each cycle of the RF oscillator. So you would use a 64-bit DAC to convert the digital data stream into an analog signal, frequency modulate ...
Mr X's user avatar
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2 answers
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Which of these 2 phenomena occur first - AN or MDIX

Most of these days, the Ethernet PHY/switch devices support Auto-MDIX and Autonegotiation. So, when a link partner is getting connected to a PHY or a Switch, which of these two phenomenons happens ...
Novice's user avatar
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Comparing between orthogonal BPSK and differential BPSK

Suppose two modulation schemes, orthogonal BPSK and differential BPSK. In orthogonal BPSK, we transmit $$\textbf{x}_{A}:= [x[0], x[1]]^{T}=[1, 0]^{T},$$ and $$\textbf{x}_{B}:= [0, 1]^{T}.$$ This ...
PSH's user avatar
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2 votes
3 answers
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What causes a digital signal to look like this?

I’m reverse engineering an existing microprocessor to microprocessor serial signal. When I put my scope on the target device I see the clock and data lines just fine on my scope when I connect it to ...
DaveInPA's user avatar
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1 answer
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Error probability of BPSK with intersymbol interference

Consider an AWGN channel with BPSK modulation. Assume that the information bits are i.i.d. Bernoulli with parameter 0<p<1, we have ISI due to a timing offset at the transmitter, and the decoder ...
Ben's user avatar
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2 votes
3 answers
179 views

Why do we need to transmit in a cable with a digital modulation? Can't we just put high voltage for 1 and no voltage for 0? [closed]

We know that we can't transmit a square wave pulse via EM and we need to convert it to an analog signal via some modulation. But why can't we just put high voltage in the cable to represent bit 1 and ...
allexj's user avatar
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What does an SD Card do internally during the 74 clock cycles at startup

It is documented that the SD Bus Interface requires 74 clock cycles before the first command is sent: Taken from SD Specifications Part 1 Physical Layer, Simplified Specification, Version 6.00 https:/...
Graham's user avatar
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1 answer
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What exactly does the limiter do in FSK demodulators?

I wonder what exactly the limiter does in FSK demodulators. What are the advantages? Could it be just a saturation in ADC or fixed-pointing stages?
Ali's user avatar
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Network bus with tree topology with network exploration

I am planing to experiment with Arduino framework to create a network of microcontrollers, where they communicate with each other. There will be one master and this should be able to explore the ...
VPNer's user avatar
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2 votes
2 answers
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Phase modulation for binary data - higher frequency harmonics?

I've recently learned about PSK and QAM. I first came across it in this youtube video (timestamped), and my understanding for how it works has remained the same as what is shown in that video. (I also ...
TrisT's user avatar
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Equidistant PAM-n symbols

Why do we choose PAM-n symbols to be equidistant ? What will happen if it's not so? Any references are welcomed !
Isha's user avatar
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1 vote
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Data availability on a HART device network configured for multi-drop mode

We have 2 flow meters on an equipment installation that are HART-capable. As they are installed today, configuring these devices in multi-drop mode would be much easier than running additional wire ...
Big Owls's user avatar
1 vote
2 answers
62 views

How accurate are internal terminators on chips with high speed differential inputs?

I'm aware that due to process variation, some analog parameters of semiconductor devices can vary; sometimes quite a lot. (E.g. the SST3904 transistor specifies a DC current gain somewhere between 100 ...
Rocketmagnet's user avatar
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1 vote
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Is BPSK better than QPSK in any way?

I wonder why there are still some modems using BPSK as their modulation. Is there any benefit over QPSK (power, bandwidth, synchronization techniques, etc.)? I have been searching and found these: ...
Ali's user avatar
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5 votes
3 answers
2k views

Best protocol for daisy chain communication between many small microcontrollers

I'm working on a project where I'd like a large number of small microcontrollers (100+, something like an 8-bit PIC, but flexible on what I use) to each perform audio synthesis behavior defined by an ...
Emmett Palaima's user avatar
18 votes
8 answers
3k views

Data transmission protocol with two lines and no explicit clock

Are there communication protocols that transmit bits using two lines A and B as follows: When line A is toggled, a 0 is sent. When line B is toggled, a 1 is sent. I currently use this to push out ...
Nordic Mainframe's user avatar
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Is the use of ethernet cables/RJ45's appropriate for high frequency applications (3GB/s, 1.5GHz )

I am looking into using a GMSL2 serializer/deserializer pair for using a CSI camera at long distances from a computer. The GMSL2 channel specifications give the following information: Firstly, I'm ...
Harrison's user avatar
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48 views

Why do we get increase in BER with increase in Eb/N0 of the signal?

I'm working on a problem of MSK modulation scheme. I have passed my modulated signal through SUI channel Models and AWGN. But As I want to do analysis on the performance of SUI channels I'm getting ...
Fatima Ismail's user avatar
1 vote
1 answer
56 views

PCM audio ADC: can the system clock be the fed with the PCM bit clock?

I'm trying to use an Iridium Core 9523N module to send the speaker output of my computer over satellite to any telephone. The integrator's guide says it accepts PCM-formatted digital audio data, and ...
user325962's user avatar
1 vote
1 answer
52 views

6GHz GMSL2 signal over UTP, calculating insertion loss over cables

I'm doing some research into having CSI cameras at a distance of around 3m from a computer and am thinking of using a CSI to GMSL2 serializer deserializer pair, in particular, the MAX96724 and ...
Harrison's user avatar
1 vote
1 answer
69 views

ADC SDO/SDI timing in daisy chain

I am trying to understand how much propagation delay of the clock signal is allowed between two AD7984 as described in AD7984 "Chain mode without busy indicator" on page 22. This is how I ...
cyrus010's user avatar
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How would one display raw input to TX pin on a HM-10 BLE module as a graph on a web app?

Basically I'm trying to feed in High low signals into the TX pin of a HM-10 BLE module and display it as a graph, similar to how an oscilloscope would, or possibly just have a threshold where it would ...
rhett a's user avatar
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2 votes
2 answers
75 views

How to handle varying chip voltages on an I2C line?

I am working on a design where I have various chips that operate at different voltages that I am trying to put on one I2C bus. Normally I'd just pick different chips that accomplish the same goal with ...
Sal's user avatar
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2 votes
2 answers
67 views

I2C BME688 Read Request Sent, but no data received

As the title suggests, im interfacing with the BME688 using I2C. The signal I captured using my logic analyzer is shown below. The slave address is 0x76 and register address im trying to read is 0xD0. ...
lrdewaal's user avatar
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0 answers
37 views

PE44820 Phase Shifter Confusion in Results

I am using a PE44820 phase shifter for my capstone project. We created our own evaluation board so that we can test it with a raspberry pi3. We are running a simple test first where we are just trying ...
Alexandria Walker's user avatar
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136 views

How fast can a Schmitt trigger operate? Can I use it for signal conditioning digital serial data?

I would like to know if I could use a Schmitt trigger chip (e.g., 74HCT14, CD40106B and 74AC14) to clean a 12MHz serial digital signal that has gone through a long cable and will pass through multiple ...
Emerson's user avatar
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0 answers
65 views

i2c boards distance

I would like to use an I2C bus between 7 boards. first board used as main with the mcu controller, Rest of the 6 with io expanders (16ch each), the distance between the main board to each board is 15c&...
barg's user avatar
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1 vote
2 answers
105 views

Can you transmit a number stored on a digital counter over a network protocol without a micro-controller? [closed]

TL;DR I am storing a 24-bit number that represents number of pulses from a clock on a digital counter IC, and want to transmit that number to a more sophisticated device to perform a speed = distance/...
cornelius's user avatar
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0 votes
2 answers
191 views

Digital signal routing for EMI/EMC

REMOVE THIS WHEN YOU ANSWER THE QUESTIONS IT ASKS YOUR DESCRIPTION IS UNCLEAR. PEOPLE MAY NOT UNDERSTAND THE QUESTION PROPERLY AND SO WASTE TIME ANSWERING IT. You talk about transcievers and devices. ...
HV16's user avatar
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1 vote
0 answers
125 views

STM32U5 SCL line stays low and hangs

I have two STM32L0 (slaves) and STM32U585 (master) MCUs. I have no issue when Slave transmits data to Master, but if Master transmits signal to Slave, it sends all the 9 clock pulses with address bits,...
amir_sh's user avatar
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0 votes
1 answer
65 views

Suggestions for robust communication between electronic modules

I have to design an industrial system that is comprised of several modules. The system consists of one "master" and several "slaves". As the roles imply, the master will coordinate ...
m4l490n's user avatar
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1 vote
0 answers
143 views

What is SAI frame synchro?

The SAI interface, as used by ST and others, includes some options which I have not been able to find any explanation of. Justme's answer provides a great explanation of frame, slot, and data size; I'...
SRobertJames's user avatar
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0 votes
0 answers
89 views

FPD Link III Layout Best Practice

I've been doing a lot of reading around FPD-Link III interfaces as I want to attempt to make my own vehicle camera system using a DS90UB960-Q1 deserialiser and a DS90UB953-Q1 serialiser, but I've hit ...
CT123's user avatar
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0 votes
1 answer
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Can I use 2 modes of I2C operation together in 1 code? For STM32F407 interfaced with MPU6050 sensor

I have my STM32F407 discovery board (master) interfaced with an MPU6050 sensor (slave) via an I2C interface, and it reads and writes data to it. My questions is, what mode of operation is the stm32 ...
DaveFenner's user avatar
2 votes
0 answers
114 views

What Exactly Is Meant by a 2nd Order Phase Locked Loop?

I'm teaching myself about polyphase clock sync for demodulation of OQPSK. An article from gnuradio.org entitled "Polyphase Clock Sync" makes references to a 2nd order loop. The context seems ...
James Strieter's user avatar
0 votes
2 answers
65 views

How do we change the digital encoding method of a signal? (eg. From Unipolar NRZ to Polar NRZ)

We have different digital encoding methods like Unipolar, Polar, Bipolar, Manchester. I was working with stm32f411re and I saw USART uses Unipolar NRZ. So how do we change this encoding methods? I ...
Yuva Adhithyan's user avatar
5 votes
3 answers
553 views

With modern connectors, is the metal shell used as a conductor?

Does the metal shell of a connector, such as USB and HDMI, serve a conducting purpose? The metal shell of my TV's HDMI terminal is corroded. Should I make effort to have it contacting and conducting ...
Puvitar's user avatar
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0 votes
1 answer
409 views

How can I connect the DVP camera output with Raspberry Pi or other MCU?

I have a MT9V034 image sensor module and I want to use its 8-bit DVP output. Does anyone know how to connect a DVP interface with a Raspberry Pi and show some graph? I have read the Raspberry Pi user ...
Cai's user avatar
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0 votes
2 answers
405 views

PIC MCC I2C setup help

I have made use of the MSSP1 in MPLABx's MCC (code configurator). I have set it up as an I2C slave device and initialized the setup in the code provided. I am making use of a MCP2221 as a master ...
Bottle's user avatar
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2 votes
2 answers
147 views

Is digital signal transmission different from square wave?

I am just getting into signal processing and am having trouble understanding where generating square-waves by means of harmonics is useful. Digital signal transmission can be achieved by changing ...
shafe's user avatar
  • 363
-1 votes
2 answers
325 views

How many UART interfaces can be used in this MCU

I want to understand how many UART interfaces can I use in this ATSAMD21 MCU. I searched for "UART" in the datasheet to find which pins and how many UART interfaces I can connect to. But I ...
Freshman's user avatar
2 votes
2 answers
233 views

The best way to light an LED at a distance

I need to control an LED (SSR) at a someway-long distance of about 20 meters (60 feet) from a microcontroller. A simple LED on/off control type where I could keep it on for a long period of time. The ...
nochkin's user avatar
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